Video signal processing apparatus

ABSTRACT

By setting an area for displaying OSD data, a high-intensity part of this area is highlighted and an area which is not to be highlighted is set. Also, by performing translucent display of the OSD data and natural-image data, an area which is not to be highlighted can be set.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a video signal processing apparatus.

2. Description of the Related Art

FIG. 8 is a block diagram showing a schematic configuration of a knownimage capturing apparatus disclosed in Japanese Patent Laid-Open No.2001-025030. In this image capturing apparatus, an image capturingdevice 1010 converts an optical image to an image signal, and an A/Dconverter 1012 converts the analog output from the image capturingdevice 1010 to a digital signal. A captured-image-signal processor 1014executes removal of color carrier, aperture correction, and gammaprocessing on the output data from the A/D converter 1012 in order togenerate a luminance signal.

Also, the captured-image-signal processor 1014 executes colorinterpolation, matrix conversion, gamma processing, and gain control onthe output data in order to generate color-difference signals, so thatvideo data in YUV format is created.

A memory interface 1016 includes a writing circuit 1016 a and a readingcircuit 1016 b for a memory 1018. The memory interface 1016 writes thevideo data from the captured-image-signal processor 1014 in the memory1018, and reads the video data stored in the memory 1018 and outputs thevideo data to a display-system signal processor 1020.

The display-system signal processor 1020 separates the video data in YUVformat into a luminance component Y and a modulation color-differencecomponent, that is, a so-called modulation chroma component C, andapplies the luminance component Y and the chroma component C to D/Aconverters 1022Y and 1022C, respectively. The D/A converter 1022Yconverts the luminance data from the display-system signal processor1020 to an analog signal, and then a low-pass filter (LPF) 1024Y removesa high-frequency noise component from the output from the D/A converter1022Y. The output from the LPF 1024Y is applied to a mixer 1026 and anLCD controller 1028. On the other hand, the D/A converter 1022C convertsthe modulation chroma data from the display-system signal processor 1020to an analog signal, and then a band-pass filter (BPF) 1024C extractsonly a frequency component of a modulation chroma component from theoutput from the D/A converter 1022C. The output from the BPF 1024C isapplied to the mixer 1026 and the LCD controller 1028.

The mixer 1026 mixes the luminance signal from the LPF 1024Y and themodulation chroma signal from the BPF 1024C so as to generate acomposite video signal. A video amplifier 1030 amplifies the compositevideo signal output from the mixer 1026 and applies the signal to a TVmonitor 1032. Accordingly, an image captured by the image capturingdevice 1010 is displayed on a screen of the TV monitor 1032.

The LCD controller 1028 converts the luminance signal Y from the LPF1024Y and the modulation chroma signal C from the BPF 1024C to an RGBsignal in accordance with a sub-carrier frequency of a quartz oscillator1034, and applies the RGB signal together with a driving pulse to aliquid crystal display (LCD) panel 1036. Accordingly, the LCD panel 1036displays the image captured by the image capturing device 1010 on itsscreen.

In this known image capturing apparatus, the dynamic range of the LCD isinsufficient to express high and low intensity. In particular, thegradation in high- and low-intensity areas of a displayed image ispoorly expressed. Therefore, it is difficult to visually checkdistortion in high- and low-intensity areas in the displayed image so asto manually adjust exposure or to compensate exposure. In order toovercome this problem, the following method has been used. That is,during a review after taking an image, a high-intensity area ishighlighted in order to clearly display the high-intensity area in theLCD.

Hitherto, in order to perform highlight display by using on screendisplay (OSD), the luminance level of each pixel of natural-image VRAMdata is measured, OSD data for highlight display is created based on themeasurement result, and then the OSD data is written in a memory. Inthis method, however, OSD data must be created every time thenatural-image VRAM data changes, and thus it takes some time to performhighlight display.

When an electronic viewfinder (EVF) is used, since the rate ofdisplaying images read by an image capturing device is high, anoperation of rewriting OSD data for highlight display cannot keep upwith the rate. Therefore, highlight display cannot be performed.

Also, at an electronic zoom operation in the EVF, the rewritingoperation cannot keep up with the changes of a zoom factor, and thushighlight display cannot be realized.

When an image is zoomed during playback, highlight display cannot beperformed in synchronization with the zoomed played back image.Therefore, the highlight display cannot be completed until some timepasses after the played back image has been zoomed.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above-describedproblems, and an object of the present invention is to provide a videosignal processing apparatus which smoothly performs highlight display byusing OSD.

In order to achieve the object, according to a preferred embodiment ofthe present invention, a video signal processing apparatus includes afirst storage unit for storing input first image data; a second storageunit for storing second image data; a first comparing unit for comparingluminance-signal component data in the first image data with apredetermined level; a modifying unit for modifying the second imagedata based on the output from the first comparing unit; and asynthesizing unit for synthesizing the first image data and the secondimage data modified by the modifying unit and outputting the synthesizeddata.

Also, according to a preferred embodiment of the present invention, byswitching OSD data to an OSD data value having a palette color forhighlight display according to the level of luminance signal of imagedata, a high-intensity part of the image data can be highlighted.

Further objects, features and advantages of the present invention willbecome apparent from the following description of the preferredembodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a schematic configuration of a videosignal processing apparatus according to a first embodiment of thepresent invention.

FIG. 2 shows the internal configuration of a FIFO 26.

FIG. 3 shows the internal configuration of a superimposing circuit 36.

FIG. 4 shows the internal configuration of a highlight display circuit32.

FIG. 5 is an image view of highlight display.

FIG. 6 is an image view of highlight display at electronic zoom.

FIG. 7 is a block diagram showing a schematic configuration of a videosignal processing apparatus according to a second embodiment of thepresent invention.

FIG. 8 is a block diagram showing a schematic configuration of a knownimage capturing apparatus.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed.

First Embodiment

A first embodiment of the present invention is described below withreference to the drawings. FIG. 1 is a block diagram showing a schematicconfiguration of a video signal processing apparatus according to thefirst embodiment of the present invention. The video signal processingapparatus includes an image capturing device 10 for converting anoptical image to an electric signal; an A/D converter 12 for convertingthe analog image signal from the image capturing device 10 to a digitalsignal; a captured-image-signal processor 14 which generates a luminancesignal by executing removal of a color carrier, aperture correction, andgamma processing on the output data from the A/D converter 12 and whichalso generates color-difference signals by executing colorinterpolation, matrix conversion, gamma processing, and gain control, soas to create video data in YUV format; and a timing generator (TG) 16which generates clocks and timing signals required by the imagecapturing device 10, the A/D converter 12, and the captured-image-signalprocessor 14 in accordance with the output from a quartz oscillator 18(the oscillation frequency is 36 MHz, for example) and which suppliesthe clocks and timing signals to the image capturing device 10, the A/Dconverter 12, and the captured-image-signal processor 14.

Also, the video signal processing apparatus includes a resizing circuit20 which resizes the image data from the captured-image-signal processor14 into a display size; and a memory interface 22 which includes awriting circuit 22a and a reading circuit 22b for a memory (DRAM) 24 andwhich writes the video data from the resizing circuit 20 in the memory24 and reads the video data stored in the memory 24. Memory space(so-called VRAM) for displaying images is allocated on the memory 24.

A method for storing image data in the VRAM includes two types:Y:U:V=4:2:2, and Y:U:V=4:1:1. Assume that each of the luminance signal Yand the color-difference signals U/V is 8-bit data. In this case, whenY:U:V=4:2:2, the data is stored in the VRAM in the following manner:

Upper-byte data=Y0, Y1, Y2, Y3, Y4, Y5, Y6, Y7, . . .

Lower-byte data=U0, V0, U2, V2, U4, V4, U6, V6, . . . .

On the other hand, when Y:U:V=4:1:1, the data is stored in the VRAM inthe following manner:

Upper-byte data=Y0, Y1, Y3, Y4, Y5, Y7, . . .

Lower-byte data=U0, V0, Y2, U4, V4, Y6, . . . .

The amount of data when Y:U:V=4:1:1 is ¾ of the amount of data whenY:U:V=4:2:2. In a bandwidth of image display in a TV monitor and an LCDpanel, Y:U:V=4:1:1 is an enough amount of information. Therefore, theVRAM, which is optimally used in terms of memory capacity and datatransfer efficiency, should be compatible with the storage method ofY:U:V=4:1:1. For this reason, the storage method of Y:U:V=4:1:1 isadopted for the VRAM in this embodiment.

For example, if the image capturing device 10 corresponds to two millionpixels, the amount of output data for each frame from thecaptured-image-signal processor 14 is equivalent to horizontal 1600pixels and vertical 1200 pixels. The resizing circuit 20 resizes theoutput data from the captured-image-signal processor 14 into a VRAM sizewhich is suitable for display, and stores the resized data in the VRAMof the memory 24.

As will be described later, in display processing at a clock of 13.5MHz, a TV display area according to the NTSC consists of horizontal 720pixels and vertical 480 lines. In order to configure VRAM data in thisscreen size, the resizing ratio of the resizing circuit 20 is set at720/1600=9/20 in the horizontal and at 480/1200=2/5 in the vertical, soas to generate VRAM data.

On the other hand, in another display size, e.g., in a TV display of aPAL method (horizontal 720 pixels and vertical 575 lines), the settingof the resizing ratio in the resizing circuit 20 is changed accordingly,that is, the resizing ratio is set at 720/1600 in the horizontal and at575/1200 in the vertical, so as to output VRAM data.

In some image capturing devices, when an electronic viewfinder (EVF) isdisplayed, the frame rate is increased by decreasing the number of linesto be read in the vertical direction to 600 lines by adding 2 lines inthe vertical direction or by skipping subsequent two lines by every twolines forming a pair. In this way, when the EVF is used, the frame rateof reading in the image capturing device is increased by performing2-pixel addition or 2-pixel skipping in the vertical direction so as todisplay the EVF in the TV monitor and LCD panel. In this case, the dataread from the image capturing device is horizontal 1600 pixels andvertical 600 lines. This data is resized into a VRAM configuration of aTV field image of horizontal 720 pixels and vertical 240 lines, so as todisplay the EVF in the TV monitor and LCD panel. The resizing ratio ofthis case is 720/1600=9/20 in the horizontal and 240/600=2/5 in thevertical, which is the same as the above-mentioned resizing ratio.

Referring back to FIG. 1, reference numeral 26 is a first-in first-out(FIFO) buffer for converting the video data output from the memoryinterface 22 to data having a different data rate. Although the detailswill be described later, the FIFO 26 converts a data sequence of 18 MHzfrom the memory interface 22 to a data sequence of 13.5 MHz, which issuitable for display in a TV monitor of an NTSC method or a PAL method.

(Explanation of the FIFO 26)

Now, the internal configuration of the FIFO 26 is described withreference to FIG. 2. A VALID flag, which indicates that write data isvalid, is input from the memory interface 22 to an input terminal 80,and the write data DATA is input from the memory interface 22 to aninput terminal 82. Further, a write clock WR_CK is input to an inputterminal 84, a read flag, which defines timing for reading data from theFIFO 26, is input to an input terminal 86, and a read clock RD_CK isinput to an input terminal 88.

When the VALID flag is 1, video data is input to the input terminal 82,and when the VALID flag is 0, no video data is input to the inputterminal 82. In this embodiment, the write clock WR_CK is a clock of 18MHz, which is obtained by dividing 36 MHz output from the TG 16. Therate of the write clock WR_CK does not always match the rate of theVALID flag. The rate of writing data into the FIFO 26 substantiallymatches the rate of reading video data from the image capturing device10, but the rate of the write clock WR_CK is irrelevant to the rate ofwriting data into the FIFO 26.

An input-data latch circuit 90 captures the data from the input terminal82 when the VALID flag is 1. A write-address generator 92 generates awrite address which is incremented according to the write clock WR_CKwhen the VALID flag is 1. A read-address generator 94 generates a readaddress which is incremented according to the read clock RD_CK when theread flag is 1.

Reference numeral 96 denotes an SRAM including a data writing port and adata reading port. The output data from the input-data latch circuit 90is input to the data writing port WR_DT, the write clock WR_CK from theinput terminal 84 is input to a write clock port WR_CK, the output fromthe write-address generator 92 is input to a write-address port WR_ADR,the read clock RD_CK from the input terminal 88 is input to a read clockport RD_CK, and the output from the read-address generator 94 is inputto a read-address port RD_ADR. The SRAM 96 writes the data from theinput-data latch circuit 90 in the location indicated by the writeaddress generated by the write-address generator 92 according to thewrite clock WR_CK.

Also, when the read flag at the input terminal 86 is 1, the SRAM 96reads data from the location indicated by the read address generated bythe read-address generator 94 according to the read clock RD_CK, andoutputs the read data from a read-data output port RD_DT. However, whenthe read flag at the input terminal 86 is 0, the SRAM 96 does not readdata. The read flag changes at a rate equal to the read clock of 13.5MHz of the FIFO 26. The read clock RD_CK is n times of 11.04 MHz,wherein n is 2 or 4. Therefore, the write clock WR_CK and the read clockRD_CK are completely asynchronous.

A luminance-signal latch circuit 98 captures luminance data in theoutput data from the SRAM 96 according to the read clock RD_CK, and thecolor-difference-signal latch circuit 100 captures color-difference datain the output data from the SRAM 96 according to the read clock RD_CK.The luminance-signal latch circuit 98 and the color-difference-signallatch circuit 100 are configured so that the output therefrom satisfiesY:U:V=4:2:2. When the VRAM on the memory 24 is configured for a dataformat of Y:U:V=4:2:2, the upper byte of the output from the SRAM 96corresponds to luminance (Y) data and the lower byte corresponds tocolor-difference (UV) data. Thus, the output data can be easilyseparated into luminance (Y) data and color-difference (UV) data bydividing the bits, so that a data format of Y:U:V=4:2:2 can be realized.When the VRAM on the memory 24 is configured for a data format ofY:U:V=4:1:1, the luminance-signal latch circuit 98 and thecolor-difference-signal latch circuit 100 are configured so that theoutput from the SRAM 96 is distinguished from each other based on theaddress and that the data format of Y:U:V=4:1:1 is converted toY:U:V=4:2:2. That is, the luminance-signal latch circuit 98 capturesluminance data in the upper and lower bytes of the output data from theSRAM 96 according to the read address, and the color-difference-signallatch circuit 100 captures color-difference data which exists only inthe lower byte of the output data from the SRAM 96 according to the readaddress. With this process, the output from the FIFO 26 can always be ina format of Y:U:V=4:2:2 regardless of the configuration of the VRAM.With this configuration of the FIFO 26, the writing data rate of 18 MHz,which is obtained by dividing the output clock of the TG 16, of theimage data captured by the image capturing device 10 is converted to arate of 13.5 MHz of the read clock of the FIFO 26. [00401 As shown inFIG. 1, the FIFO 26 includes a FIFO 26 a for a natural image and a FIFO26 b for OSD. In the two FIFOs, the capacity of the SRAM 96 is differentfrom each other due to the difference in the data size of each pixel.However, the amount of FIFO pixels for each screen is almost the same.Also, the function and operation are almost the same in the two FIFOs.

Referring back to FIG. 1, delay circuits 28 and 30 serve for adjustingtiming. Each delay circuit includes a flip-flop (FF) and delays data inthe unit of a clock of 13.5 MHz. In this case, the delay circuits 28 and30 delay the luminance signal Y and the color-difference signals U/Vfrom the FIFO 26 according to a circuit delay in a highlight displaycircuit 32 and a palette converter 34, which will be described later.

The highlight display circuit 32 serves for highlighting high-intensityand low-intensity parts of natural image data from the image capturingdevice 10 by using a function of on screen display (hereinafter referredto as OSD). The internal configuration of the highlight display circuit32 is described below with reference to FIG. 4.

(Explanation of the Highlight Display Circuit 32)

FIG. 4 shows the internal configuration of the highlight display circuit32 shown in FIG. 1. Hereinafter, the highlight display circuit 32, whichhighlights high-intensity and low-intensity parts of natural image datafrom the image capturing device 10 by using the function of OSD, will bedescribed with reference to FIG. 4.

In FIG. 4, reference numeral 200 denotes input of the luminance signalof the natural image from the FIFO 26 shown in FIG. 1. The luminancesignal has a data width of 8 bits. Reference numeral 202 denotes inputof the OSD signal from the FIFO 26, and the OSD signal has a data widthof 4 bits. Reference numeral 204 denotes a register including an 8-bitFF, in which a threshold of a high-intensity level is set. Referencenumeral 206 denotes a comparator which compares the level of the input200 and the value of the register 204. The comparator 206 outputs a1-bit flag signal of 1 when the level of the input 200 is larger, andoutputs a 1-bit flag signal of 0 when the level of the input 200 issmaller. Reference numeral 208 denotes a register including a 1-bit FF.The flag signal output from the comparator 206 is allowed to passthrough an exclusive-OR circuit 210. When the register 208 is 0, theflag signal from the comparator 206 is noninverted and thehigh-intensity part of the natural image is highlighted. When theregister 208 is 1, the flag signal from the comparator 206 is invertedand the low-intensity part of the natural image is highlighted.

Reference numeral 212 denotes a register including a 4-bit FF, in whicha basic OCD value for performing highlight display is set. Referencenumeral 214 denotes a comparator for matching which compares the OSDdata from the input 202 and the value of the register 212 and outputs 1when the both values match. Reference numeral 216 denotes an AND circuitfor performing an AND operation of the output from the exclusive-ORcircuit 210, which outputs a result flag of a high-intensity leveldetecting circuit system, and the output from the comparator 214, whichoutputs a result flag of a circuit system for determining the basic OSDvalue. The corresponding pixel when the output of the AND circuit 216 is1 is a pixel to be highlighted.

Reference numeral 218 denotes a blink counter which counts every twocycles (2V) of a TV vertical synchronization signal.

When the NTSC method is used, Time of1V=1/fv;fv=(2/525)×(4500000/286)=59.94 Hz, and 1V=16.683 msec; and2V=33.366 msec. Therefore, the counter counts every 33.36 msec.

When the PAL method is used, Time of 1V=1/fv;fv=50 Hz, and 1V=20 msec;and 2V=40 msec. Therefore, the counter counts every 40 msec.

The blink counter 218 includes a register for setting a blink cycle. Thevalue set in the register is used as a counter cycle of the blinkcounter, and switching between 1 and 0 is performed at every cycle ofthe counter so as to output a flag signal. The flag signal output fromthe blink counter 218 is input to one of input terminals of an ORcircuit 222. Also, the output from a BLINK_ON register 220 including a1-bit FF is input to the other inversion input terminal of the ORcircuit 222. When the BLINK_ON register 220 is 0, the output from the ORcircuit 222 is always 1 regardless of the flag signal output from theblink counter 218, and thus blink is not performed. On the contrary,when the BLINK_ON register 220 is 1, the status of the flag signaloutput from the blink counter 218 is output to the OR circuit 222, sothat blink is performed.

Reference numeral 224 denotes an AND circuit which outputs the AND ofthe signals from the AND circuit 216 and the OR circuit 222. A selector228 is switched based on the output from the AND circuit 224. Theselector 228 switches between the input of OSD data 202 and the data ofa HIP_PLT register 226. The selector 228 outputs the OSD data from theinput 202 when being set to 0 and outputs the data from the HIP_PLTregister 226 when being set to 1. The data from the HIP_PLT register 226is data of OSD in which a palette color for high intensity or lowintensity is set. A palette converter 34 shown in FIG. 4 corresponds toa palette converter 34 shown in FIG. 1, which serves as a circuit forconverting the OSD data to palette data, as described above. Palettedata generated in the palette converter 34 is output from a terminal230.

That is, highlight display herein means a function of detecting whetherthe luminance level of a target pixel is higher or lower than apredetermined level, replacing the pixel with OSD of high-intensitybased on the detection result, and displaying blink or the like based onwhether or not the pixel is replaced with OSD.

Referring back to FIG. 1, the palette converter 34 is a circuit forconverting OSD data of characters and icons to palette data having aratio of Y:U:V=4:2:2, in which Y is 8 bits and UV is 8 bits.

However, when the OSD data is expressed with 65536 colors, in which eachof Y and UV is 8 bits, as in natural-image data captured by the imagecapturing device, the amount of data of each pixel is too large, andthus a large memory capacity for the OSD data is required accordingly.In addition, the amount DRAM data to be read for display (bandwidth ofDRAM) is significantly lost. For these reasons, the colors forexpressing the OSD data must be reduced and effective OSD must beperformed on the TV monitor and LCD panel. The amount of OSD data isless than that of natural-image data. Hereinafter, a case where 16colors (4 bits) can be simultaneously generated and 65536 colors (16bits) can be expressed will be described.

When 16 colors are simultaneously generated, that means each pixel ofthe OSD data stored in the memory 24 consists of 4 bits. When the sizeof VRAM (e.g., TV display in the NTSC method) is horizontal 720pixels×vertical 480 lines, the amount of data is 720×480×4 bits=172800bits, which is about a quarter of the amount of natural-image data fromthe image capturing device 10.

Specifically, in order to realize expression with 65536 colors (16bits), 16 palette registers each having a 16-bit width are provided inthe circuit so that one of the 16 palette registers can be selectedbased on the value indicated by the OSD data. That is, the number ofcolors which are simultaneously generated in one screen depends on thebit width of the OSD data, and the number of colors in the palettedepends on the bit width of a palette register. In this configuration,the number of colors which are simultaneously generated is limited whilemaintaining the number of colors in the palette, so that the amount ofdata in the OSD area is reduced.

Herein, colors in the palette consist of Bit 15|Bit 14|Bit 13|Bit 12|Bit11|Bit 10|Bit 9|Bit 8|T_SW|Y(6)|Y(5)|Y(4)|Y(3)|Y(2)|Y(1)|Y(0)|Bit 7|Bit6|Bit 5|Bit 4|Bit 3|Bit 2|Bit 1|Bit0|U(7)|U(6)|U(5)|U(4)|V(7)|V(6)|V(5)|V(4)|.

The bit of T_SW serves as a switch flag between translucent display andnon-transparent display. The gradation of the luminance signal Y of OSDconsists of 7 bits, and each of the color-difference signals U and Vconsists of 4 bits. With these colors, considerably practical OSD can beperformed.

In FIG. 1, reference numeral 36 denotes a superimposing circuit forsuperimposing the OSD data including characters on the natural-imagedata from the image capturing device 10. In this circuit configuration,a transparent color is assigned to one of the colors in the palette(e.g., FF00h) and the original natural image is output as is for thetransparent part. Accordingly, an OSD image and a natural image can bedisplayed in units of pixels. Furthermore, by providing a selector,which selects whether or not to perform superimposing, at the outputstage of the superimposing circuit 36 and by switching the selector soas to output only a natural image, only the natural image can bedisplayed without superimposing OSD data thereon. The internalconfiguration of the superimposing circuit 36 is described below withreference to FIG. 3.

(Explanation of the Superimposing Circuit 36)

FIG. 3 shows the internal configuration of the superimposing circuit 36.In FIG. 3, reference numeral 110 denotes an input of luminance data (8bits) of a natural image, and reference numeral 112 denotes an ON/OFFcontrol signal of superimposing (Y_SP_ON). The ON/OFF control signal isY_SP_ON=0 in a case of a transparent color in the above-describedpalette converter, and is Y_SP_ON=1 in a case of other than atransparent color so as to perform superimposing. In order to forcefullyturning OFF superimposing, Y_SP_ON is set to 0.

In FIG. 3, reference numeral 114 denotes an input of color-differencedata (8 bits) of a natural image, and reference numeral 116 denotes anON/OFF control signal of superimposing (UV_SP_ON). As in the luminancesignal, the ON/OFF control signal is UV_SP_ON=0 in a case of atransparent color in the above-described palette converter, and isLT_SP_ON=1 in a case of other than a transparent color so as to performsuperimposing. In order to forcefully turning OFF superimposing,UV_SP_ON is set to 0.

In FIG. 3, reference numeral 118 denotes an input of luminance data (7bits) of OSD. By shifting the luminance data to the left by 1 bitimmediately after the input, the level thereof is matched to the data ofthe upper 7 bits of the luminance data (8 bits) of the natural image.Reference numeral 120 denotes color-difference data (4 bits) of OSD. Byshifting the color-difference data to the left by 4 bits immediatelyafter the input, the level thereof is matched to the data of the upper 4bits of the color-difference data (8 bits) of the natural image.

Further, reference numeral 122 denotes a switch which is switched basedon the bit of the above-mentioned T_SW. When T_SW=0, translucent displayis performed, and when T_SW=1, non-transparent display is performed. Inthe translucent display, the luminance data of the natural image isshifted to the right by 2 bits so as to reduce the level thereof to ¼and the luminance data is input to an adder 124, which adds theluminance data of the natural image and the luminance data of OSD. Inthe non-transparent display, the luminance data of the natural image isnot input to the adder 124, but only the luminance data of OSD is outputthrough the adder 124. Reference numeral 126 denotes a limiter forlimiting the data width of 9 bits obtained in the adder 124 to a datawidth of 8 bits. Reference numeral 128 denotes a switch which isswitched based on the above-mentioned Y_SP_ON signal. The luminancesignal from the switch 128 is output from an output terminal 140.

Reference numeral 132 also denotes a switch which is switched based onthe bit of the above-mentioned T_SW, as the switch 122. When T_SW=0,translucent display is performed, and when T_SW=1, non-transparentdisplay is performed. In the translucent display, the color-differencedata of the natural image is shifted to the right by 2 bits so as toreduce the level thereof to ¼ and the color-difference data is input toan adder 134, which adds the color-difference data of the natural imageand the color-difference data of OSD. In the non-transparent display,the color-difference data of the natural image is not input to the adder134, but only the color-difference data of OSD is output through theadder 134. Reference numeral 136 denotes a limiter for limiting the datawidth of 9 bits obtained in the adder 134 to a data width of 8 bits.Reference numeral 138 denotes a switch which is switched based on theabove-mentioned UV_SP_ON signal. The color-difference signal from theswitch 138 is output from an output terminal 142.

Referring back to FIG. 1, a synchronizer 38 synchronizescolor-difference sequential signals, and an encoder 42 performs chromaencoding compatible with the NTSC method or the PAL method.

A delay circuit 40 delays the luminance signal Y in accordance with aprocessing delay of the synchronizer 38 and the encoder 42.

A D/A converter 44 converts the digital luminance signal Y to an analogsignal, and a D/A converter 46 converts the encoded digital chromasignal to an analog signal.

Reference numeral 70 denotes an output terminal for the analog luminancesignal, and reference numeral 72 denotes an output terminal for theanalog chroma signal, each corresponding to the output of ASIC(application-specific integrated circuit).

A low-pass filter (LPF) 50 removes high-frequency noise of the analogluminance signal after D/A conversion, and a band-pass filter (BPF) 52removes high- and low-frequency noise of the analog chroma signal afterD/A conversion.

A mixer 54 mixes the analog luminance signal from the LPF 50 and theanalog chroma signal from the BPF 52 and generates a video compositesignal to be displayed on a TV monitor 58. A video amplifier 56amplifies the video composite signal so as to have the amplitude andoutput impedance according to a TV standard and outputs the signal. TheTV monitor 58 displays a visible image generated based on the compositevideo signal from the video amplifier 56.

A quartz oscillator 60 generates a sub-carrier, which is used fordecoding the encoded chroma signal into color-difference signals. An LCDcontroller 62 converts the luminance signal Y and the chroma signal C toa signal to be displayed in an LCD panel 64 and generates timing ofdisplay. The LCD panel 64 displays a visible image based on theluminance signal Y and the chroma signal C.

The LCD controller 62 converts the luminance signal Y from the LPF 50and the modulation chroma signal C from the BPF 52 to an RGB signalaccording to the sub-carrier frequency from the quartz oscillator 60 andapplies the RGB signal together with a driving pulse to the LCD panel64. The LCD panel 64 displays the image captured by the image capturingdevice 10 on the screen thereof.

(Operation 1)

Hereinafter, a case where highlight display is performed in an EVFbefore taking a picture will be described.

The image capturing device 10 shown in FIG. 1 operates so as tosequentially read each field of captured data in horizontal 1600+αpixels×vertical 600+β lines. The A/D converter 12 converts thesequential analog data from the image capturing device 10 to digitaldata and input the data to the captured-image-signal processor 14. The“+α” is extra pixels (32 to 64 pixels) required by a filter in thehorizontal direction, and the “+P” is extra lines (3 to 6 lines)required by a filter in the vertical direction.

The captured-image-signal processor 14 generates a luminance signal Yand color-difference signals U and V in the above-described processing,creates video data in Y:U:V=4:2:2 format of horizontal 1600pixels×vertical 600 lines, and inputs the video data to the resizingcircuit 20. The resizing circuit 20 resizes the video data inY:U:V=4:2:2 format of horizontal 1600 pixels×vertical 600 lines, whichhas been supplied from the captured-image-signal processor 14, with aresizing ratio of 9/20 in the horizontal pixels and 2/5 in the verticallines, and then outputs the data in Y:U:V=4:1:1 format of horizontal 720pixels×vertical 240 lines to the memory I/F 22. The memory I/F 22prepares two VRAM data areas, each for video data of horizontal 720pixels×vertical 240 lines, on the memory 24. Then, the memory I/F 22writes the first field of the resized data from the resizing circuit 20in one of the VRAM data areas and writes the second field of the resizeddata in the other VRAM data area. In this way, the two VRAM data areasare alternately rewritten by each field. When the memory I/F 22 iswriting VRAM data, it reads the VRAM data which is not being written atthe same time and outputs the VRAM data to the FIFO 26. At this time, ifthe VRAM data which is being written is read and displayed, temporallyshifted data is displayed at the border of the written data, and thus anunsightly image will be displayed. For this reason, the two VRAM dataareas are provided on the memory 24 in order to separate the write VRAM(active VRAM) and the read VRAM (view VRAM). Further, several frames ofdata for OSD are stored in the memory 24. In an area for OSD, data(simultaneously-generated color of 16 colors in 4 bits in each pixel)for displaying current time (month-day-year and hour-minute-second) andpicture-taking information is stored.

The VRAM data in Y:U:V=4:1:1 format and the OSD data read by the memoryI/F 22 are written in the FIFO 26. Then, according to theabove-described operation of the FIFO 26, a luminance signal Y,color-difference signals U and V, and OSD data are separately output ata data rate of 13.5 MHz. The luminance signal Y is input to the delaycircuit 28, the color-difference signals U and V are input to the delaycircuit 30, and the OSD data is input to the highlight display circuit32.

In the highlight display circuit 32, basic OSD data is set to CMP_PLT ofthe register 212 shown in FIG. 4, and the data value of the palette setto a high-intensity color is set to HIP_PLT of the register 226. Forexample, when HIP_PLT of the register 226 is set to 3, a colorlesshigh-intensity palette color is generated by setting the luminance to 70H and each of U and V to 00 H for the palette color of OSD data 3, sothat a palette color particularly suitable for highlight display is set.Then, according to the output flag of the AND circuit 224, OSD data 0set to a transparent palette color and OSD data 3 set to ahigh-intensity color are switched by the selector 228. Then, the outputtherefrom is converted to a palette color for highlight in the paletteconverter 34.

Referring to FIG. 1, the output from the palette converter 34, theluminance signal Y output from the delay circuit 28, and thecolor-difference signals U and V output from the delay circuit 30 areinput to the superimposing circuit 36. Then, as described above, thesignals from the superimposing circuit 36 are processed in thesynchronizer 38, the encoder 42, and the D/A converters 44 and 46, sothat an analog luminance signal and a modulation chroma signal areoutput, and then a-visible image is displayed on the LCD panel 64.

Now, a display state will be described with reference to an image viewof highlight display shown in FIG. 5. The outermost solid-line framedefines an image display area of the LCD panel, and the innerbroken-line frame defines an area of OSD data=0. By setting CMP_PLT ofthe register 212 to 0, highlight display is performed in high-intensityparts (parts indicated by arrows) of this area. An area defined by adotted line at the upper right portion of FIG. 5 is set to OSD data=2.In this area, OSD data and natural-image data are displayedtranslucently. This area is used for displaying date and time and is nothighlighted. In this way, by specifying basic OSD data, the area forhighlight display can be limited, and information about picture takingand the like is not highlighted but is kept in a clear condition. Then,by setting the blink counter 218 to 1 to 2 seconds and setting theBLINK_ON register 220 to 1, blink of highlight display and originalnatural-image display is performed in the highlight areas, so that theoperator can visually understand a message in a high-intensity part inthe EVF.

(Operation 2)

Next, a case where highlight display is performed in an image enlargedby electronic zoom will be described.

FIG. 6 shows an image view of electronic zoom. Reference numeral 312 inFIG. 6 denotes an image displayed on the LCD panel when the electroniczoom is set to a wide angle. In this wide image 312, many outsidebuildings are shown, and high-intensity parts, such as a surfacereflecting sunlight of the buildings and clouds, are highlighted. Byzooming the wide image 312 by electronic zoom, an image 314 can beobtained.

The operation of electronic zoom is realized by changing the resizingratio of the resizing circuit 20 shown in FIG. 1. For example, the datasize of the wide image 312 after being processed by thecaptured-image-signal processor 14 is horizontal 1600 pixels×vertical600 lines. By resizing this data to 9/20 in the horizontal and 2/5 inthe vertical, the data in Y:U:V=4:1:1 format of horizontal 720pixels×vertical 240 lines is output from the resizing circuit 20. Then,the resized data is displayed in the LCD, as described above. On theother hand, the image 314 is obtained by zooming the central part of thewide image 312 at 4× magnification. At this time, the output from thecaptured-image-signal processor 14 is horizontal 400 pixels×vertical 150lines. The resizing ratio of the resizing circuit 20 is set to 9/5 inthe horizontal and 8/5 in the vertical, so as to generate VRAM data ofhorizontal 720 pixels×vertical 240 lines.

Then, the data read from the memory 24 including VRAM is input to theFIFO 26, where the data rate is converted from 18 MHz to 13.5 MHz andthe data is separated into a luminance signal Y and color-differencesignals U and V, which are then output. The data of the luminance signalY and the color-difference signals U and V output from the FIFO 26 isoutput as an enlarged image of the wide image 312. Further, the OSD datain the memory 24 is read by the reading circuit 22 b of the memory I/F22, the rate thereof is converted by the FIFO 26, and then the OSD datais output to the highlight display circuit 32. Herein, the same OSD dataas that described in the Operation 1 is read from the FIFO 26 and isinput to the highlight display circuit 32. Therefore, as described abovewith reference to FIG. 5, the area of OSD data=0 is highlighted. Thearea of OSD data=2 at the upper right of FIG. 6, which displays the dateand time, is not highlighted and is clearly displayed.

When highlight display is performed in the known OSD circuit, OSD datafor highlight display is created according to the luminance level ofeach pixel of natural-image VRAM data and the OSD data is written in thememory 24. Therefore, the OSD data must be created every time thenatural-image VRAM data changes. On the other hand, in the highlightdisplay circuit of the present invention, whether or not highlightdisplay is performed is automatically determined based on the level ofthe luminance signal Y of a natural image read from the FIFO 26.Accordingly, when the size of image of an object changes by electroniczoom, pixels to be highlighted are switched by following the change inreal time.

The OSD data output from the highlight display circuit 32 is input tothe palette converter 34, and is converted to a luminance signal Yosdand color-difference signals UVosd for expressing palette colors. Theoutput therefrom is input to the superimposing circuit 36, where theluminance signal Yosd-and color-difference signals uvosd are mixed withthe luminance signal Y and the color-difference signals UV of thenatural image, so that a highlight display is superimposed. After that,as described above, the signals are processed by the synchronizer 38,the encoder 42, and the D/A converters 44 and 46 so that an analogluminance signal and modulation chroma signal are output, and then avisible image is displayed on the LCD panel 64.

Second Embodiment

Next, highlight display during playback is described with reference toFIG. 7.

In FIG. 7, the circuit configuration except a medium card 400 and adecompressing circuit 402, that is, the configuration from the resizingcircuit 20 to the output terminal 72 is the same as in the firstembodiment shown in FIG. 1. Also, parts denoted by the same referencenumerals as in FIG. 1 have completely the same function andcharacteristic as in FIG. 1. The medium card 400 is a removablerecording medium, such as a CF card, and stores captured image datawhich is compressed according to a standard, such as JPEG (JointPhotographic Experts Group).

The decompressing circuit 402 is a circuit for decompressing compressedimage data supplied from the medium card 400. The decompressing circuit402 decompresses an image of horizontal 1600 pixels×vertical 1200 lineswhich has been compressed according to a JPEG standard and inputs thedecompressed data to the resizing circuit 20 in the subsequent stage.The resizing circuit 20 is the same as that in the first embodiment,creates VRAM data (frame image) in Y:U:V=4:1:1 format of horizontal 720pixels×vertical 480 lines at a resizing ratio of 9/20 in the horizontaland 2/5 in the vertical, and writes the resized data in the memory 24through the memory I/F 22.

The operation thereafter is the same as that in the first embodiment.OSD data as well as the VRAM exists in the memory 24. The memory I/F 22reads the natural-image data in Y:U:V=4:1:1 format in the VRAM and theOSD data from the memory 24 through the reading circuit 22 b and outputsthe data to the FIFO 26. The FIFO 26 separates the natural-image data ofthe VRAM into a luminance signal Y and color-difference signals U and V,and also outputs the OSD data while absorbing it to the FIFO buffer. Theluminance signal Y and the color-difference signals U and V of thenatural image from the FIFO 26 are delayed by the delay circuits 28 and30, respectively, so as to be synchronized with the output of the OSDdata from the palette converter 34. On the other hand, the OSD data inthe FIFO 26 is replaced in the highlight display circuit 32 byrecognizing that a pixel of a predetermined value or more of theluminance signal Y of the natural image is a pixel to be highlighted. Apalette color for highlight display is assigned to the replaced OSDdata, and the OSD data is converted to a luminance signal Yosd andcolor-difference signals UVosd in the palette converter 34. Theluminance signal Y and the color-difference signals U and V of thenatural image are superimposed on the luminance signal Yosd and thecolor-difference signals UVosd by the superimposing circuit 36, and theabove-mentioned natural image Y of a high-intensity part is highlightedby the OSD of highlight display. Then, as described above, the signalsare processed by the synchronizer 38, the encoder 42, and the D/Aconverters 44 and 46 so that an analog luminance signal and a modulationchroma signal are output, and a visible image is displayed on the LCDpanel 64.

When the image shown in FIG. 5 is played back by the configuration shownin FIG. 7, high-intensity parts in the area of OSD data=0 at the upperpart of FIG. 5 are highlighted, and the area of OSD=2 which displays thedate and time at the upper right in FIG. 5 is not highlighted even ifthe intensity of the natural image is high. Accordingly, thehigh-intensity part of a played back image is displayed visuallyclearly, and supplementary information such as the date of picturetaking is clearly displayed without being affected by highlight display.

Next, highlight display at zooming during playback is described withreference to FIGS. 6 and 7.

FIG. 6 was used for explaining electronic zoom in the EVF. Also, FIG. 6can be applied to a case where compressed data of an image of outsidebuildings stored in the medium card 400 is played back by using theconfiguration shown in FIG. 7. The compressed data of an image ofoutside buildings is read from the medium card 400, the data isdecompressed by the decompressing circuit 402, and an image ofY:U:V=4:2:2 of horizontal 1600 pixels×vertical 1200 lines is output tothe resizing circuit 20. The resizing circuit 20 resizes the image atthe resizing ratio of 9/5 in the horizontal and 8/5 in the vertical soas to realize 4× magnification used in the above case, and outputs imagedata in Y:U:V=4:1:1 format of horizontal 2880 pixels×1920 lines, so asto write the image data in the VRAM of the memory 24. The readingcircuit 22 b in the memory I/F 22 reads data corresponding to horizontal720 pixels×vertical 480 lines at the center of the image data ofhorizontal 2880 pixels×1920 lines. The read data corresponds to theimage 314 shown in FIG. 6. After that, as described above, the data orsignals are processed by the FIFO 26, the delay circuits 28 and 30, thehighlight display circuit 32, the palette converter 34, thesuperimposing circuit 36, the synchronizer 38, the encoder 42, and theD/A converters 44 and 46. Accordingly, an analog luminance signal and amodulation chroma signal are output, and a visible image is displayed onthe LCD panel 64.

In this way, images can be zoomed during playback only by changing theresizing ratio of the resizing circuit 20. Also, highlight display canbe performed in real time without rewriting OSD data.

As described above, highlight display can be performed in real timewithout rewriting OSD data according to the level of a luminance signalof image data captured by the image capturing device. Therefore,highlight display can be performed for an image displayed in an EVF.

Also, even when image data is scaled up/down by electronic zoom, pixelimage data of OSD in DRAM need not be rewritten. Therefore, real-timehighlight display can be performed according to the magnification ofelectronic zoom.

Also, by keeping highlight display ON/OFF for a predetermined period byusing the incorporated counter, blinking of highlight can be performedwithout rewriting data.

Further, by using a circuit for switching the output of a resultobtained by comparing the level of the luminance signal of the imagedata with a predetermined value set to the register toinversion/noninversion, the dark portion (low-intensity level) of theimage data can be highlighted.

Still further, in a played back image, highlight display whichimmediately responds to the change of images can be performed.Furthermore, when a played back image is scaled up/down, highlightdisplay which immediately responds to the change of zoom magnificationcan be performed.

While the present invention has been described with reference to whatare presently considered to be the preferred embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments. On the contrary, the invention is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims. The scope of the following claims is to beaccorded the broadest interpretation so as to encompass all suchmodifications and equivalent structures and functions.

This application claims priority from Japanese Patent Application No.2003-422338 filed Dec. 19, 2003, which is hereby incorporated byreference herein.

1. A video signal processing apparatus comprising: A) first storagemeans for storing input first image data; B) second storage means forstoring second image data; C) first comparing means for comparingluminance-signal component data in the first image data with apredetermined level; D) modifying means for modifying the second imagedata based on the output from the first comparing means; and E)synthesizing means for synthesizing the first image data and the secondimage data modified by the modifying means and outputting thesynthesized data.
 2. A video signal processing apparatus according toclaim 1, wherein the first image data is a captured-image signalobtained by capturing a natural image and the second image data is OSDimage data.
 3. A video signal processing apparatus according to claim 2,wherein the first comparing means determines a high-intensity area or alow-intensity area based on the luminance level of the first image dataand the modifying means replaces the high-intensity area or thelow-intensity area with the second image data.
 4. A video signalprocessing apparatus according to claim 1, wherein the modifying meansgenerates different patterns for the high-intensity area, thelow-intensity area, and a normal-intensity area of the first image data,and superimposes the patterns on the first image data.
 5. A video signalprocessing apparatus according to claim 4, wherein the modifying meansblinks the second image data, in which the blink cycle is variable.
 6. Avideo signal processing apparatus comprising: A) resizing means forresizing input image data; B) first storage means for storing the imagedata output from the resizing means and OSD data; C) second storagemeans which temporarily stores the image data and OSD data read from thefirst storage means, which is capable of asynchronously executingwriting and reading, and which separately reads luminance-signalcomponent data and chroma-signal component data of the image data andthe OSD data; D) first comparing means for comparing theluminance-signal component data read from the second storage means witha predetermined level; E) second comparing means for comparing the OSDdata read from the second storage means with a predetermined value; F)selector means for switching between the OSD data read from the secondstorage means and the predetermined value based on the AND of an outputresult from the first comparing means and an output result from thesecond comparing means; G) converting means for converting the outputfrom the selector means to luminance-signal component data andchroma-signal component data of the OSD data; and H) superimposing meansfor superimposing the luminance-signal component data and thechroma-signal component data of the image data from the second storagemeans on the luminance-signal component data and the chroma-signalcomponent data of the OSD data from the converting means.
 7. A videosignal processing apparatus according to claim 6, further comprising acounter which switches output of 0 and 1 at a time interval that can bearbitrarily changed, wherein the selector means is switched based on theAND of the output from the counter and a switching condition of theselector means.
 8. A video signal processing apparatus according toclaim 7, further comprising switching means for switching logic of theoutput from the first comparing means to inversion or noninversion.
 9. Avideo signal processing apparatus according to claim 8, furthercomprising: image capturing means for converting an image of a subjectto an electric signal; A/D converting means for converting the outputfrom the image capturing means to a digital signal; and signalprocessing means for processing the output from the A/D converting meansso as to generate a luminance signal and color-difference signals,wherein the output from the signal processing means is input to theresizing means.
 10. A video signal processing apparatus according toclaim 7, further comprising: a removable recording medium for recordingencoded image data; and decoding means for decoding the encoded imagedata which is output from the recording medium, wherein the output fromthe decoding means is input to the resizing means.
 11. A video signalprocessing apparatus according to claim 10, wherein the decoding meansdecompresses compressed image data of JPEG format.